AQP4 and obstructive hydrocephalus: Increased AQP4 microvesicle expression was confirmed with flow cytometry in which the mean fluorescence intensity of AQP4 was significantly higher in samples from patients with obstructive hydrocephalus, (41.13; p < 0.01) compared to samples from patients with communicating hydrocephalus (15.87; p < 0.01) or control (15.86; p > 0.05).